1. Field of the Invention
The present invention relates to a slide surface construction and particularly, to a slide surface construction formed of an aggregate of metal crystals and a process for producing the same.
2. Description of the Related Art
There are conventionally known slide surface constructions. Typical examples of such known slide surface constructions are: 1) a Pb alloy plated layer provided on the inner peripheral surface of a rolled-steel back plate of a slide bearing for an internal combustion engine, which is opposed to a rotary shaft, for the purpose of enhancing the seizure resistance; 2) various plated layers provided on an inner peripheral surface of a cylinder sleeve made of a cast iron in a combination of a piston made of an aluminum alloy and such cylinder sleeve in an internal combustion engine for the purpose of enhancing the slide characteristic; and 3) an Fe-plated layer provided on outer peripheral surfaces of a land portion and a skirt portion of a piston body made of an aluminum alloy in a piston for an internal combustion engine for purpose of enhancing the wear resistance.
However, the above known slide surface constructions suffer from a problem that under existing circumstances where speed and output of the internal combustion engine have tended to increase, the known slide surface construction is not sufficient in oil retaining property, namely, oil retention and poor in seizure resistance due to a relatively smooth slide surface thereof.
There is also a conventionally known slide surface construction which is formed on an engagement surface of a gear in a gearing device by roughening the engagement surface by machining or the like, and then applying a solid lubricating agent such as molybdenum disulfide, graphite and the like, or a semi-solid lubricating agent such as grease onto the roughened engagement surface, so that latter retains the lubricating agent.
However, the known engagement surface is simple in view of microstructure and has a problem that it is low in solid lubricating agent retention and the like and, as a result, is poor in seizure resistance under a high load condition.
Therefore, the present assignee has previously developed a slide surface construction which is formed on an inner peripheral surface of a backing plate, an inner peripheral surface of a cylinder sleeve, an outer peripheral surface of a piston body, an engagement surface of a gear and the like, and which includes a large number of pyramid-shaped metal crystals in the slide surface thereof (see Japanese Patent Application Laid-open No. 174089/94).
If the slide surface construction is formed in the above manner, adjacent pyramid-shaped metal crystals assume mutually biting states and hence, the slide surface takes on an intricate aspect comprising a large number of fine crests, a large number of fine valleys formed between the crests, and a large number of swamps formed due to the mutual biting of the crests. Therefore, the slide surface construction is improved in oil retention and in solid lubricating agent retention and the like and thus, has an enhanced seizure resistance.
In the above-described slide bearing, however, the following situation has been encountered: when two regions suitable under different sliding conditions are produced in the slide surface construction, even if one of the two regions exhibits a good sliding characteristic under a severe sliding environment, it cannot be expected that the other region exhibits such a good sliding characteristic, because the slide characteristic of the slide surface construction is substantially constant over the entire region thereof.
As for the gearing device, it has been ascertained that in order to accommodate the severe sliding environment, for example, where a sudden and excessively large variation in load occurs in the gear, it is necessary to further enhance the solid lubricating agent retention of the slide surface construction.
As for the cylinder sleeve, it has been ascertained that when the viscosity of the oil is high, for example, at a lower temperature, the flow of the oil lacks a smoothness, resulting in a relatively high dynamic friction coefficient .mu. and for this reason, the friction loss tends to be increased.
Further, as for the piston, it has been also ascertained that in order to accommodate the severe sliding environment, it is necessary to further enhance the oil retention of the slide surface construction to reduce the solid contact to the utmost, thereby further enhancing the seizure resistance, and to reduce the dynamic friction coefficient .mu. to further enhance the wear resistance.